1. Field of the Invention
The present invention relates to a liquid crystal display. More particularly, the present invention relates to a method and apparatus for driving a liquid crystal display that facilitates the setting and maintenance of display parameters and improves a picture quality of a liquid crystal display panel.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) controls light transmittance characteristics of liquid crystal cells in accordance with externally applied video signals to thereby display a picture. Active matrix type LCDs include switching devices (i.e., thin film transistors (TFTs)) formed at each liquid crystal cell and are used as monitors for computers, office equipment, cellular phones, and the like.
FIG. 1 schematically illustrates a related art LCD driving apparatus.
Referring to FIG. 1, the related art LCD driving apparatus generally includes a liquid crystal display panel 2 having m×n number of liquid crystal cells (Clc) arranged in a matrix pattern, m number of data lines D1 to Dm, n number of gate lines G0 to Gn crossing the m number of data lines D1 to Dm, TFTs provided at the crossings of the gate and data lines, a data driver 4 for applying data signals to the data lines D1 to Dm, a gate driver 6 for applying scanning signals to the gate lines G1 to Gn, a gamma voltage supplier 8 for supplying gamma voltages to the data driver 4, a timing controller 10 for controlling the data and gate drivers 4 and 6 using synchronizing signals output from system 20, a direct current to direct current (DC/DC) converter 14 for generating voltages supplied to the liquid crystal display panel 2 using a voltage output from a power supply 12, and an inverter 16 for driving aback light 18.
The system 20 applies vertical/horizontal signals Vsync/Hsync, clock signals DCLK, a data enable signal DE, and red, green, and blue video data R, G and B to the timing controller 10.
Provided at each of the liquid crystal cells, the TFTs apply data signals from the data lines D1 to Dm to the liquid crystal cells in response to scanning signals transmitted by the gate lines G1 to Gn. Further, each liquid crystal cell includes a storage capacitor Cst to maintain a voltage charged to the liquid crystal cell. The storage capacitor Cst is provided either between a pixel electrode of the liquid crystal cell Clc and a pre-stage gate line or between the pixel electrode of the liquid crystal cell Clc and a common electrode line.
As mentioned above, the gamma voltage supplier 8 applies a plurality of gamma voltages to the data driver 4. The data driver 4 converts video data R, G and B into analog data voltages (i.e., data signals) using the applied gamma voltages in response to control signals CS output from the timing controller 10. The data driver 4 further applies the data signals to the data lines D1 to Dm.
The gate driver 6 sequentially applies scanning pulses to the gate lines G1 to Gn in response to control signals CS output from the timing controller 10. Upon application of the scanning pulses, horizontal lines of liquid crystal cells within the liquid crystal display panel 2 are supplied with data signals.
The timing controller 10 generates control signals CS to control the gate and data driver 6 and 4 using vertical/horizontal synchronizing signals Vsync and Hsync and the clock signal DCLK output from the system 20. Control signals CS that control the gate driver 6 include a gate start pulse GSP, a gate shift clock GSC, and a gate output enable signal GOE. Control signals CS that control the data driver 4 include a source start pulse SSP, a source shift clock SSC, a source output enable signal SOE, and a polarity signal POL. Further, the timing controller 10 re-aligns video data R, G and B output from the system 20 and applies the re-aligned data to the data driver 4.
The DC/DC converter 14 raises or lowers a voltage of 3.3V output from the power supply 12 to generate voltages suitable for driving the liquid crystal display panel 2. Accordingly, the DC/DC converter 14 generates a gamma reference voltage, a gate high voltage VGH, a gate low voltage VGL, and a common voltage Vcom.
The inverter 16 applies a driving voltage (or driving current) to drive the back light 18. Upon receiving the driving voltage (or driving current), the back light 18 generates light. The generated light is subsequently emitted to the liquid crystal display panel 2.
Driving the liquid crystal panel 2 as described above is undesirable, however, because defective images are displayed when brightness and chrominance components of input video data R, G and B are above or below reference value ranges.